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<div id="projectbrief">Set of algorithms implemented in C.</div>
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<p><a href="https://projecteuler.net/problem=14" target="_blank">Problem 14</a> solution
<a href="#details">More...</a></p>
<div class="textblock"><code>#include &lt;stdio.h&gt;</code><br />
<code>#include &lt;stdlib.h&gt;</code><br />
<code>#include &lt;omp.h&gt;</code><br />
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Include dependency graph for sol1.c:</div>
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Functions</h2></td></tr>
<tr class="memitem:a81c1df5c17cb16bcc16e346fcff6fa80"><td class="memItemLeft" align="right" valign="top">long long&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d4/dea/problem__14_2sol1_8c.html#a81c1df5c17cb16bcc16e346fcff6fa80">collatz</a> (long long start_num)</td></tr>
<tr class="memdesc:a81c1df5c17cb16bcc16e346fcff6fa80"><td class="mdescLeft">&#160;</td><td class="mdescRight">Computes the length of collatz sequence for a given starting number. <a href="../../d4/dea/problem__14_2sol1_8c.html#a81c1df5c17cb16bcc16e346fcff6fa80">More...</a><br /></td></tr>
<tr class="separator:a81c1df5c17cb16bcc16e346fcff6fa80"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:a3c04138a5bfe5d72780bb7e82a18e627"><td class="memItemLeft" align="right" valign="top">int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d4/dea/problem__14_2sol1_8c.html#a3c04138a5bfe5d72780bb7e82a18e627">main</a> (int argc, char **argv)</td></tr>
<tr class="memdesc:a3c04138a5bfe5d72780bb7e82a18e627"><td class="mdescLeft">&#160;</td><td class="mdescRight">Main function. <a href="../../d4/dea/problem__14_2sol1_8c.html#a3c04138a5bfe5d72780bb7e82a18e627">More...</a><br /></td></tr>
<tr class="separator:a3c04138a5bfe5d72780bb7e82a18e627"><td class="memSeparator" colspan="2">&#160;</td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p ><a href="https://projecteuler.net/problem=14" target="_blank">Problem 14</a> solution </p>
<dl class="section author"><dt>Author</dt><dd><a href="https://github.com/kvedala" target="_blank">Krishna Vedala</a></dd></dl>
<p>Since the computational values for each iteration step are independent, we can compute them in parallel. However, the maximum values should be updated in synchrony so that we do not get into a "race condition".</p>
<p >To compile with supporintg gcc or clang, the flag "-fopenmp" should be passes while with Microsoft C compiler, the flag "/fopenmp" should be used. If you are using the provided CMAKE compilation, it will automatically detect OPENMP and compile with it for you.</p>
<p >Automatically detects for OPENMP using the _OPENMP macro. </p>
</div><h2 class="groupheader">Function Documentation</h2>
<a id="a81c1df5c17cb16bcc16e346fcff6fa80" name="a81c1df5c17cb16bcc16e346fcff6fa80"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a81c1df5c17cb16bcc16e346fcff6fa80">&#9670;&#160;</a></span>collatz()</h2>
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<td class="memname">long long collatz </td>
<td>(</td>
<td class="paramtype">long long&#160;</td>
<td class="paramname"><em>start_num</em></td><td>)</td>
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<p>Computes the length of collatz sequence for a given starting number. </p>
<div class="fragment"><div class="line"><span class="lineno"> 28</span>{</div>
<div class="line"><span class="lineno"> 29</span> <span class="keywordtype">long</span> <span class="keywordtype">long</span> length = 1;</div>
<div class="line"><span class="lineno"> 30</span> </div>
<div class="line"><span class="lineno"> 31</span> <span class="keywordflow">while</span> (start_num != 1) <span class="comment">/* loop till we reach 1 */</span></div>
<div class="line"><span class="lineno"> 32</span> {</div>
<div class="line"><span class="lineno"> 33</span> <span class="keywordflow">if</span> (start_num &amp; 0x01) <span class="comment">/* check for odd */</span></div>
<div class="line"><span class="lineno"> 34</span> start_num = 3 * start_num + 1;</div>
<div class="line"><span class="lineno"> 35</span> <span class="keywordflow">else</span></div>
<div class="line"><span class="lineno"> 36</span> start_num &gt;&gt;= 1; <span class="comment">/* simpler divide by 2 */</span></div>
<div class="line"><span class="lineno"> 37</span> length++;</div>
<div class="line"><span class="lineno"> 38</span> }</div>
<div class="line"><span class="lineno"> 39</span> </div>
<div class="line"><span class="lineno"> 40</span> <span class="keywordflow">return</span> length;</div>
<div class="line"><span class="lineno"> 41</span>}</div>
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<a id="a3c04138a5bfe5d72780bb7e82a18e627" name="a3c04138a5bfe5d72780bb7e82a18e627"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a3c04138a5bfe5d72780bb7e82a18e627">&#9670;&#160;</a></span>main()</h2>
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<td class="memname">int main </td>
<td>(</td>
<td class="paramtype">int&#160;</td>
<td class="paramname"><em>argc</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">char **&#160;</td>
<td class="paramname"><em>argv</em>&#160;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
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<p>Main function. </p>
<div class="fragment"><div class="line"><span class="lineno"> 45</span>{</div>
<div class="line"><span class="lineno"> 46</span> <span class="keywordtype">long</span> <span class="keywordtype">long</span> max_len = 0, max_len_num = 0;</div>
<div class="line"><span class="lineno"> 47</span> <span class="keywordtype">long</span> <span class="keywordtype">long</span> MAX_NUM = 1000000;</div>
<div class="line"><span class="lineno"> 48</span> </div>
<div class="line"><span class="lineno"> 49</span> <span class="keywordflow">if</span> (argc ==</div>
<div class="line"><span class="lineno"> 50</span> 2) <span class="comment">/* set commandline argumnet as the maximum iteration number */</span></div>
<div class="line"><span class="lineno"> 51</span> {</div>
<div class="line"><span class="lineno"> 52</span> MAX_NUM = atoll(argv[1]);</div>
<div class="line"><span class="lineno"> 53</span> printf(<span class="stringliteral">&quot;Maximum number: %lld\n&quot;</span>, MAX_NUM);</div>
<div class="line"><span class="lineno"> 54</span> }</div>
<div class="line"><span class="lineno"> 55</span> </div>
<div class="line"><span class="lineno"> 56</span> <span class="keywordtype">long</span> <span class="keywordtype">long</span> i;</div>
<div class="line"><span class="lineno"> 57</span><span class="preprocessor">#ifdef _OPENMP</span></div>
<div class="line"><span class="lineno"> 58</span><span class="preprocessor">#pragma omp parallel for shared(max_len, max_len_num) schedule(guided)</span></div>
<div class="line"><span class="lineno"> 59</span><span class="preprocessor">#endif</span></div>
<div class="line"><span class="lineno"> 60</span> <span class="keywordflow">for</span> (i = 1; i &lt; MAX_NUM; i++)</div>
<div class="line"><span class="lineno"> 61</span> {</div>
<div class="line"><span class="lineno"> 62</span> <span class="keywordtype">long</span> <span class="keywordtype">long</span> <a class="code hl_struct" href="../../df/db3/struct_l.html">L</a> = <a class="code hl_function" href="../../d4/dea/problem__14_2sol1_8c.html#a81c1df5c17cb16bcc16e346fcff6fa80">collatz</a>(i);</div>
<div class="line"><span class="lineno"> 63</span> <span class="keywordflow">if</span> (<a class="code hl_struct" href="../../df/db3/struct_l.html">L</a> &gt; max_len)</div>
<div class="line"><span class="lineno"> 64</span> {</div>
<div class="line"><span class="lineno"> 65</span> max_len = <a class="code hl_struct" href="../../df/db3/struct_l.html">L</a>; <span class="comment">/* length of sequence */</span></div>
<div class="line"><span class="lineno"> 66</span> max_len_num = i; <span class="comment">/* starting number */</span></div>
<div class="line"><span class="lineno"> 67</span> }</div>
<div class="line"><span class="lineno"> 68</span> </div>
<div class="line"><span class="lineno"> 69</span><span class="preprocessor">#if defined(_OPENMP) &amp;&amp; defined(DEBUG)</span></div>
<div class="line"><span class="lineno"> 70</span> printf(<span class="stringliteral">&quot;Thread: %2d\t %3lld: \t%5lld\n&quot;</span>, omp_get_thread_num(), i, <a class="code hl_struct" href="../../df/db3/struct_l.html">L</a>);</div>
<div class="line"><span class="lineno"> 71</span><span class="preprocessor">#elif defined(DEBUG)</span></div>
<div class="line"><span class="lineno"> 72</span> printf(<span class="stringliteral">&quot;%3lld: \t%5lld\n&quot;</span>, i, <a class="code hl_struct" href="../../df/db3/struct_l.html">L</a>);</div>
<div class="line"><span class="lineno"> 73</span><span class="preprocessor">#endif</span></div>
<div class="line"><span class="lineno"> 74</span> }</div>
<div class="line"><span class="lineno"> 75</span> </div>
<div class="line"><span class="lineno"> 76</span> printf(<span class="stringliteral">&quot;Start: %3lld: \tLength: %5lld\n&quot;</span>, max_len_num, max_len);</div>
<div class="line"><span class="lineno"> 77</span> </div>
<div class="line"><span class="lineno"> 78</span> <span class="keywordflow">return</span> 0;</div>
<div class="line"><span class="lineno"> 79</span>}</div>
<div class="ttc" id="aproblem__14_2sol1_8c_html_a81c1df5c17cb16bcc16e346fcff6fa80"><div class="ttname"><a href="../../d4/dea/problem__14_2sol1_8c.html#a81c1df5c17cb16bcc16e346fcff6fa80">collatz</a></div><div class="ttdeci">long long collatz(long long start_num)</div><div class="ttdoc">Computes the length of collatz sequence for a given starting number.</div><div class="ttdef"><b>Definition:</b> sol1.c:27</div></div>
<div class="ttc" id="astruct_l_html"><div class="ttname"><a href="../../df/db3/struct_l.html">L</a></div><div class="ttdef"><b>Definition:</b> list.h:8</div></div>
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